The present invention relates to a position detecting method, a position detecting apparatus, an exposure method, an exposure apparatus, a computer readable recording medium and a device manufacturing method. More particularly, the present invention relates to the position detecting method and the position detecting unit for detecting positions of plural divided areas formed on an object; the exposure method and the apparatus for using the position detecting method; the computer readable recording medium in which the programs to be executed are stored; and a device manufacturing method for using the exposure method.
Conventionally, in a lithographic process for manufacturing a semiconductor device, liquid crystal display device and so forth, an exposure apparatus has been used. In such an exposure apparatus, patterns formed on a mask or reticle (to be genetically referred to as a xe2x80x9creticlexe2x80x9d hereinafter) are transferred through a projection optical system onto a substrate such as a wafer or a glass plate (to be referred to as a xe2x80x9csubstrate or waferxe2x80x9d herein after, as needed) coated with a resist or the like. As the exposure apparatus, a static exposure type projection exposure apparatus such as a so-called stepper, or a scanning exposure type one such as a so-called scanning stepper is generally used.
In these exposure apparatus, prior to exposure, the positioning of the reticle and the wafer (alignment) must be precisely performed. In order to perform the alignment, position detection marks formed in the above-mentioned lithographic process, i.e., alignment marks formed by exposure transfer, are associates to each shot area. Therefore, the position of the wafer or the circuit pattern on the wafer might be detected by detecting the alignment mark. Then, the alignment is performed by using the detection result of the position of the wafer or the circuit pattern on the wafer.
At present, several methods for position detecting of the alignment mark on the wafer is practically used. Recently, the position detecting method depends on the image detection became major. In this method, optical images of the alignment marks are picked-up by using the image pick-up unit, and the signal of the picked-up image, that is, the distribution of light intensity of the image is then analyzed to detect the positions of the alignment marks. As procedures for such waveform analysis, there is a pattern matching procedure (a template matching). In this method, the position of the alignment of which image is picked-up is set to a parameter, and the correlation between the parameter and the template waveform previously prepared is investigated in the image pick-up range for the alignment mark. Signal waveforms are analyzed by the pattern matching procedure, and the parameter value with the highest correlation between the template waveform is obtained. By using the parameter value, the position of the alignment marks is precisely detected.
The method, which is based on the template matching of the above-mentioned mark image pick-up signal (to be referred to as a xe2x80x9craw waveformxe2x80x9d hereinafter, as needed) and used in the conventional method, has high tolerance to the noise having enough smaller period than the arrangement pitch of the line pattern (to be referred to as a xe2x80x9chigh frequency noisexe2x80x9d, hereinafter). For example, when the mark is structured as the line and space mark, the position detection of the mark is precisely performed by using the template matching of the raw waveform, even though the high frequency noise is superposed on the image pick-up signal. The line and space mark is composed of plural line pattern arranged in the predetermined intervals and direction. This derives from that the template matching has a averaging effect of the noise, and the effect caused by the high frequency noise is effectively deleted by the averaging effect of such noises.
However, the noise superposed on the image pick-up signal is not limited to the high frequency noise. For example, in the line and space mark, the noise which has the same degree of the arrangement frequency of the line mark or higher one (to be referred to as a xe2x80x9clow frequency noisexe2x80x9d, hereinafter) sometimes superposed on the image pick-up signal. In this case, the effect of the noise caused by the averaging effect from the template matching of the raw waveform can not be efficiently removed. Accordingly, the position detection of the mark can not be precisely performed by using the raw waveform template matching, when the low frequency noise is superposed on the image pick-up signal.
The purpose of the present invention is to provide the position detecting methods and the apparatuses thereof for detecting the positional information of the mark formed on the object.
The another purpose of the present invention is to provide the exposure method and the exposure apparatus for transferring the predetermined pattern to the object accurately.
The yet another purpose of the present invention is to provide the computer readable recording medium in which a program for precisely detecting the positional information of the mark formed on the object is stored.
The still another purpose of the present invention is to provide the device manufacturing method for manufacturing the highly integrated device with fine patterns.
The present inventors have been studied the detection for the position detection mark consisting of line patterns and line spaces formed on the substance and used for positioning. In light of this, the following knowledge is obtained: it is important to detect the border between the line part and the space part (to be referred to as the xe2x80x9cedgexe2x80x9d, hereinafter), at which the signal level of the imaging signal (i.e., signal intensity) is drastically changed in the position detection of the mark; and it is possible to detect the edge position by detecting the position, at which the absolute value of the rate of change in the signal waveform of the imaging signal is maximum, or the point of inflection in the signal waveform of the imaging signal. The other knowledge is also obtained: that is, the width of the edge portion is very narrow comparing to the line or space width, and the waveform of the edge portion is effected when the high frequency noises are superposed, but not affected when the low frequency noises are superposed. The present invention is completed based on the above mentioned knowledge.
In the first aspect of the present invention, the present invention is a position detecting method for detecting a positional information of a mark formed on an object comprising the steps of: performing an image pick-up of the mark; obtaining a predetermined order differential waveform of a signal waveform, which is obtained in the image pick-up; and detecting said positional information of the mark, based on a correlation between said differential waveform and a predetermined template waveform.
According to this, the imaging signal of the mark obtained is differentiated, and the predetermined order differentiated waveform of the imaging signal is obtained. The differentiated waveform is obtained by focusing on the edge, which is less effected by the low frequency noises derived from the drastically changed signal level of the imaging signal. For example, the rate of change for the signal level of the image pick-up signal (imaging signal) depending on the position is obtained as a waveform, when the predetermined differential waveform is the first order waveform. Since the waveform with the drastic change of the signal level of the imaging signal is obtained, and the waveform showing the characteristics of the edge portion is obtained. Furthermore, the rate of change for the signal level of the image pick-up signal depending on the position is obtained as a waveform, when the predetermined differential waveform is the second order waveform. Therefore, the waveform showing the characteristics of the edge portion is obtained. Still further, the waveform showing the characteristics of the edge portion is obtained, even through third or higher order differential waveform is used as the predetermined differential waveform. The positional information of the mark is detected by using the template matching of thus obtained predetermined differential waveform showing the characteristics of the edge portion.
Accordingly, the positional information of the mark is precisely detected, when the low frequency noises are superposed on the image pick-up signal of the mark and the positional information of the mark can not be detected precisely by using the template matching of the raw waveform.
In the first position detecting method of the present invention, the positional information of the mark might be obtained by using the method comprising the steps of: obtaining a correlation coefficient between said differential waveform and said template waveform at a respective relative position while the relative positional relation between the differential waveform and the template waveform is changing; and detecting said positional information of the mark based on the relative positional relation at which a correlation coefficient is maximum.
In the second aspect of the present invention, the present invention is a position detecting method for detecting a positional information of a mark formed on an object comprises the steps of: performing an image pick-up of the mark; performing a predetermined modification processing to a signal waveform which is obtained by the image pick-up to obtain at least one of a modified waveform; obtaining respective mark information with respect to a position of said mark based on the respective signal waveform and the modified waveform; and detecting said positional information of said mark based on a plurality of the mark information out of the obtained mark information.
With this, the raw waveform of the imaging signal is obtained, and at least one of the modified waveform of the imaging signal is obtained. Then, the mark information for the mark position such as estimated mark position and so forth is obtained by using the respective raw waveform and at least one of the modified waveform. The positional information of the mark is detected based on the plural mark information n the obtained mark information. Accordingly, the waveform to be used for detecting the positional information of the mark is properly selected depending on the figure of the noise signal superposed on the imaging signal, and the positional information of the mark is detected by using the selected waveform. Therefore, in spite of the figure of the noise signal, mark position might be precisely detected. In the plural waveforms to be used for detecting the positional information of the mark, the raw waveform might be included or not.
In the second position detecting method of the present invention, said modified waveform might be that having different signal intensity distribution from those of said signal waveform.
In the second position detecting method of the present invention, said predetermined modification processing might include performing to change a distribution of frequency components of said signal waveform. Alternatively, said predetermined modification processing might include obtaining at least predetermined order differential waveform of said signal waveform.
At least one of the modified waveform might be the plurality order of differential waveforms up to said predetermined order.
In the second position detecting method of the present invention, said positional information of said mark is detected by using an weighted calculating operation of the plurality of mark information, in said detection for the positional information of the mark.
Respective weight of a plurality of mark information used in said weighted calculating operation can be obtained based on the plurality of the mark information and a reference mark information previously obtained.
In the detection of the positional information of the mark, a correlation coefficient at a respective relative position might be obtained, while said relative positional relation between said signal waveform and a template waveform for the signal waveform, and the relative positional relation between at least one of desirable modified waveform and the template waveform for the modified waveform in the modified ones are changing; and respectively obtaining estimated positions of the mark might be obtained based on the relative positional relation at which the correlation coefficients are maximum, wherein the estimated positions of the mark are the mark information for signal waveform of the mark or at least one of desirable modified waveform in the modified ones.
In the position detecting method of the present invention for performing the weighted calculating operation, all of said signal waveform and modified one might be used as a waveform for position detection to obtain the positional information of said mark, in a detection of said positional information of the mark.
Weights of a plurality of said mark might be obtained based on the same number of a reference mark information as those of said waveform for position detection.
The weights of a plurality of said mark information are statistically obtained based on the larger number of a reference mark information than those of said waveform for position detection.
In the second position detecting method according to the present invention, a waveform, which is estimated that it becomes the closest mark information to said reference mark information is decided to use it as the waveform for a position detection, and said mark position might be detected based on the estimated waveform for the position detection, in detecting said positional information of said mark.
In the third aspect of the present invention, the present invention is the position detecting unit for detecting a positional information of a mark formed on an object comprises an image pick-up unit for performing an image pick-up on an area formed on the object; a differentiation operating unit, which is electrically connected to the image pick-up unit, and which obtains a predetermined order differential waveform of the mark obtained as a result of the image pick-up by the image pick-up unit; and a position operating unit, which is electrically connected to the image differentiation operation unit, and which detects the positional information of the mark, based on a correlation between the differential waveform and a predetermined template waveform.
With this, the image pick-up signal (the raw waveform) is differentiated by the differentiation operating unit to obtain the predetermined order differentiation signal. The position operating unit performs the template matching the differentiation signal obtained with the template waveform. That is, the positional information of the mark might be detected by using the first position detecting method of the present invention. Accordingly, the position of the mark formed on the substance might be detected by using the first position detecting method of the present invention. Therefore, the positional information of the mark might be detected precisely by using the method, even when the low frequency noises are superposed on the imaging signals of the mark and the position detection can not be performed precisely by using the template matching of the raw waveform.
In the first position detecting unit of the present invention, said position operating unit comprises a correlation coefficient calculating unit which obtains a correlation coefficient between said differential waveform and said template waveform at respective relative position, while relative positional relation between the differential waveform and said template waveform is changing; and a position calculating unit, which is electrically connected to the correlation coefficient calculating unit, and which calculates the positional information of the mark based on the relative positional relation at which the correlation coefficient is maximum.
In the fourth aspect of the present invention, the present invention is the second position detecting unit for detecting a positional information of a mark formed on an object comprises an image pick-up unit which performs an image pick-up on the object; a waveform modifying unit which is electrically connected to the image pick-up unit, and which performs a predetermined modification processing to a signal waveform obtained as a result of the image pick-up by the image pick-up unit to obtain a modified waveform; and a mark information calculating unit which is electrically connected to the waveform modifying unit, and which obtains respective mark information with respect to a position of the mark based on a signal waveform and the modified waveform obtained by said waveform modifying unit; and a position calculating unit, which is electrically connected to the mark information calculating unit, and which detects said positional information of said mark based on a plurality of the mark information out of the mark information obtained by the mark information calculating unit.
With this, the imaging signal (the raw waveform) and the modified waveform are obtained, wherein the raw waveform is obtained from the image of the mark which is picked-up by the image pick-up unit, and the modified waveform is obtained through the modification of the imaging signal by the waveform modifying unit. Based on respective raw waveform and modified waveform, the mark information calculating unit obtains the mark information for the mark position such as estimated mark position and so forth. Then, the position calculating unit detects the positional information of the mark based on the plural mark information in the obtained mark information. That is, the waveform to be used to detect the positional information of the mark is properly selected depending on the figure of the noise signal superposed on the imaging signal, and the positional information of the mark is detected by using the selected waveform. Accordingly, the positional information of the mark might be detected by using the second position detecting method of the present invention, in spite of the figure of the noise signal, mark position might be precisely detected.
In the second position detecting unit of the present invention, said waveform modifying unit might comprise (a) a frequency component changing unit which performs a processing to change a distribution of a frequency component of said signal waveform as said predetermined modification processing, or (b) a differentiation operating unit which obtains at least predetermined order differential waveform of said signal waveform as said predetermined modification processing.
The differentiation unit is structured so that said differentiation operating unit obtains a plurality of order differential waveform up to said predetermined order, and said position calculating unit detects said positional information of said mark by using a weighted calculating operation of a plurality of the mark information.
Said position calculating unit might comprise a weight calculating unit which obtains respective weight of a plurality of said mark information used in said weighted calculating operation based on a plurality of the mark information and a reference mark information previously obtained.
In the fifth aspect of the present invention, the present invention is an exposure method to transfer a predetermined pattern onto a divided area on a substrate comprising the steps of: detecting a position information of a mark for position detection formed on the substrate by using the position detecting method according to the present invention, and obtaining a predetermined number of parameter for said predetermined divided area, and calculating an arrangement information of the divided area formed on the substrate; and transferring the pattern onto the divided area, while the position of the substrate is regulated based on the arrangement information of the divided area.
With this, in the calculation of the arrangement information, a position detection mark formed on the substrate is detected by using the method of the present invention to calculate the arrangement coordinate of the divided area on the substrate based on the detection result. Then, in the transfer process, the pattern is transferred onto the divided area, while the positioning of the substrate is preformed based on the calculation result of the arrangement information of the divided area calculated.
In the sixth aspect of the present invention, the present invention is an exposure apparatus for transferring a predetermined pattern onto a divided area on a substrate comprising: a stage unit which moves the substrate along a movement plane; and a position detecting unit according to this invention, which detects a position information of a mark formed on the substrate, loaded on the stage unit. According to this, the position detecting unit of the present invention might precisely detect the positional information of the mark on the substrate, further the positional information of the substrate. Accordingly, a stage unit might move the substrate along a movement plane. As a result, the predetermined pattern can be transferred onto the divided area on the substrate with improved accuracy.
In the seventh aspect of the present invention, the present invention is the first computer readable recording medium containing data for a control program to be executed by a position detecting unit to detect a mark position formed on a substrate, wherein the control program comprises the procedure to obtain a predetermined order differential waveform of a signal waveform which is obtained by the image pick-up of the mark; and the procedure to detect a positional information of the mark, based on the correlation between said differential waveform and said predetermined template waveform.
With this, the position detecting unit reads out the control program contained in the computer readable medium to execute it, the mark position on the substance might be measured by using the second position detecting method of the present invention. Accordingly, the positional information of the mark might be detected precisely by using the method, even when the low frequency noises are superposed on the imaging signals of the mark and the position detection can not be performed precisely by using the template matching of the raw waveform.
In the eighth aspect of the present invention, the present invention is the second computer readable recording medium containing data for a control program to be executed by a position detecting unit to detect a mark position formed on a substrate, wherein the control program contains the procedure to perform the predetermined modification processing to a signal waveform which is obtained by said image pick-up of the mark to obtain at least one of modified waveform; the procedure to obtain the mark information of said position mark based on said signal waveform and at least one of modified waveform respectively; and the procedure to detect the positional information of the mark based on a plurality of the mark information in the mark information previously obtained.
With this, the position detecting unit reads out the control program contained in the computer readable medium to execute it, the mark position on the substance might be measured by using the second position detecting method of the present invention. Accordingly, the positional information of the mark might be detected precisely by using the method, even when the low frequency noises are superposed on the imaging signals of the mark and the position detection can not be performed precisely by using the template matching of the raw waveform.
The present invention is the device manufacturing method using the exposure methods of the present invention in the above-mentioned lithography step. According to this, since the predetermined patterns are exposed by the present exposure method to transfer precisely onto the divided area, the productivity of the highly integrated device having the fine circuit pattern might be enhanced.